WDPN31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (EIGHT)   
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.1N 151.3E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 423 NM EAST-NORTHEAST OF ANDERSEN AFB,
     GUAM
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS LOW-LEVEL
CLOUD LINES WRAPPING TIGHTLY INTO A WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC) LENDING HIGH CONFIDENCE TO THE INITIAL
POSITION AND TRACK MOTION. RECENT MSI INDICATES TROPICAL DEPRESSION 
(TD) 08W HAS SLOWED SIGNIFICANTLY OVER THE PAST FEW HOURS AND APPEARS 
TO BE QUASI-STATIONARY. ANIMATED WATER VAPOR RGB IMAGERY INDICATES 
DRY AIR OVER THE WESTERN SEMICIRCLE WITH MOIST LOW-MID LEVEL AIR OVER
THE EASTERN AND NORTHEASTERN QUADRANTS. A 222004Z SSMIS 91 GHZ
MICROWAVE IMAGE REVEALS AN EXPOSED LLCC WITH FORMATIVE CONVECTIVE
BANDS OVER THE EASTERN SEMICIRCLE. THE INITIAL INTENSITY OF 25 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE AND IS HEDGED JUST BELOW THE
DVORAK INTENSITY ESTIMATES BASED ON THE OVERALL CONVECTIVE
STRUCTURE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: COMPETING STEERING INFLUENCE WITH A
LOW-LEVEL STEERING RIDGE POSITIONED TO THE WEST AND EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 08W IS EXPECTED TO TRACK SLOWLY WEST-
SOUTHWESTWARD OVER THE NEXT 24 HOURS BECOMING QUASI-STATIONARY WITHIN 
THE COMPETING STEERING ENVIRONMENT THROUGH TAU 36. DUE TO THE 
PRESENCE OF EXTENSIVE DRY AIR, TD 08W IS FORECAST TO SLOWLY INTENSIFY 
THROUGH TAU 36. AFTER TAU 36, THE NEAR-EQUATORIAL RIDGE WILL BUILD TO 
THE SOUTHEAST, ACCELERATING THE SYSTEM NORTHEASTWARD. AFTER TAU 72, A 
DEEP-LAYERED SUBTROPICAL RIDGE WILL ASSUME THE PRIMARY STEERING 
INFLUENCE AND WILL TURN THE SYSTEM ONTO A NORTHWESTWARD TRAJECTORY 
THROUGH TAU 120. ENVIRONMENTAL CONDITIONS SHOULD IMPROVE, ESPECIALLY 
POLEWARD OUTFLOW, ALLOWING THE SYSTEM TO REACH A PEAK INTENSITY OF 55 
KNOTS BY TAU 120.         

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 72 SHOWING A NORTH-NORTHEASTWARD TO NORTHEASTWARD
TRAJECTORY. AFTER TAU 72, THERE IS INCREASING SPREAD AND
UNCERTAINTY LENDING LOW CONFIDENCE TO THE JTWC TRACK FORECAST. THE
221800Z GFS ENSEMBLE (GEFS) SHOWS THE BULK OF THE SOLUTIONS
INDICATING A SIMILAR TRAJECTORY, HOWEVER, THERE ARE ABOUT 20
PERCENT OF THE SOLUTIONS TRACKING THE SYSTEM WESTWARD OVER THE
NORTHERN MARIANAS. RELIABLE INTENSITY GUIDANCE INDICATES PEAK
INTENSITY VALUES RANGING FROM 35 TO 80 KNOTS, WHICH REFLECTS A
FAIRLY COMPLEX, EVOLVING UPPER-LEVEL PATTERN IN THE EXTENDED FORECAST 
PERIOD. THE CURRENT JTWC INTENSITY FORECAST IS CONSERVATIVE OR AT 
LEAST SKEPTICAL OF SOME OF THE HIGHER PEAK INTENSITY ESTIMATES DUE TO 
THE MARGINAL ENVIRONMENTAL CONDITIONS EXPECTED OVER THE NEXT FEW 
DAYS. HOWEVER, THERE IS A POSSIBILTY OF RAPID INTENSIFICATION (RI) 
OCCURRING LATER IN THE FORECAST PERIOD AFTER TAU 96 AS INDICATED IN 
THE 221200Z COAMPS-TC ENSEMBLE, WHICH SHOWS RI PROBABILITIES 
INCREASING TO 40 TO 60 PERCENT.           

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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